Automobiles are a transportation means with high mobility, and are frequently the top choice for outdoor traveling. To increase driving safety, automobiles are installed with headlights, which illuminate the road ahead and prevent rear approaching vehicles from rear-end collisions. In general, vehicle headlights are available in two choices—white light and yellow light. White light headlights provide better illumination effects at nighttime as well as better visual breadth and visibility. However, in harsh weather conditions, such as in the rain and fog, white light beams may be easily reflected due to physical optical properties, hence resulting in significantly reduced visibility. Yellow headlights, although capable of preventing severe reflection issues in conditions of the fog and rain and providing better visibility, provide less satisfactory illumination effects compared to white light headlights in general nighttime with clear skies.
To solve the above issue, in some current designs, white light is used as light sources of headlights, whereas yellow light is used as light sources of fog lights. In general nighttime with clear skies, the light sources of headlights may be used for illumination; in rainy or foggy nights, the light sources of fog lights are additionally turned on to increase visual visibility. Nonetheless, the main function of the fog lights are to assist illumination instead of entirely replacing the headlights. Moreover, with the white light headlights and yellow light fog lights simultaneously turned on when the driver drives in rainy weather, the issue that the visibility is affected by the reflection of white light by rain water still persists.
Therefore, light devices with adjustable color temperature are developed. For example, the U.S. Pat. No. 8,274,230 discloses “LED Lamp Apparatus and Method for Adjusting Color Temperature of LED Module therein”. The above disclosure includes a plurality of LED strings, a plurality of drivers respectively corresponding to the LED strings, and a controller electrically connected to the drivers. The controller sends a plurality of signals to the drivers, which then modulate output currents according to the signals to adjust the color temperature of the LED strings.
However, the color temperature of the above lamp apparatus needs to be manually switched. That is, when the above lamp apparatus is used as vehicle headlights, the driver needs to manually switch the color temperature. When the ambient environment changes, in addition to paying attention to road conditions ahead, the driver also needs to manually switch the headlights, causing driver distraction and higher risks of accidents. In the event of accidental and unintentional switching under panic, for example, switching to white light having a higher color temperature in pouring rain, driving safety may also be affected. Therefore, there is a need for a solution that prevents accidents due to driver distraction and affected driving safety due to unintentionally switching vehicle headlights.